Paleoceanographic reconstruction of the NE shelf of Australia: Insights from surface and subsurface dynamics of the East Australian Current

This study examines marine sediment samples from Ocean Drilling Program Site 1195, Hole B (Lat 20°24.28'S; Long 152°40.24'E; water depth 420 m), located beneath the present-day pathway of the East Australian Current (EAC) on the shelf of Northeast Australia. The EAC represents the western boundary current of the South Pacific subtropical gyre. It originates from the bifurcation of the southern arm of the South Equatorial Current between 15°S and 20°S. The East Australian Current's evolution is linked to the tectonic reorganization of the Indonesian Gateway and the expansion of the West Pacific Warm Pool over geological time. Our analysis of foraminiferal relative abundance data revealed the existence of high surface productivity and reduced subsurface productivity during the 7.5–6.4 Ma Our findings suggest that the northward movement of Papua New Guinea may have commenced after 6.4 Ma, inferred from the consistent thinning of the mixed layer and shallowing of the thermocline. This aligns with the hypothesis proposing the formation of the New Guinea Coastal Undercurrent, potentially caused by the entrapment of a significant portion of the South Equatorial Current against the Papua boundaries, directing it northward. Additionally, we observe a significant decline in the relative abundance of Globigerinoides ruber and a shoaling of the thermocline during the Mid-Pleistocene Transition, coinciding with high surface productivity.